Optical modulators are commonly used in communications applications. A variety of these modulators use a depletion region to achieve high-speed modulation. For instance, these phase modulators often include a waveguide that has an n-type doped region and a p-type doped region positioned such that a depletion region is formed in the waveguide when a bias is not applied to the modulator. The modulator is tuned by applying a reverse bias to the modulator. The reverse bias changes the size of the depletion region. The depletion region has a different index of refraction than the surrounding light-transmitting region. As a result, changing the size of the depletion region changes the speed at which the light signal travels through the waveguide. Accordingly, the speed of the light signal through the waveguide can be tuned by tuning the bias level applied to the modulator. Tuning the speed at which the light signal travels through the waveguide allows the modulator to be employed as a phase modulator.
Many of these modulators often have an undesirably high level of optical loss as a result of the structures that are used to apply the reverse bias to the waveguide. As a result, there is a need for an optical modulator having improved loss characteristics.